The present invention relates to a plasma processing apparatus that processes a substrate-like sample such as a semiconductor wafer arranged in a processing chamber in a vacuum vessel using plasma formed in the processing chamber, and relates to a plasma processing apparatus in which an electric field propagating in a waveguide arranged above the vacuum vessel is introduced into the processing chamber to form the plasma.
As an apparatus that produces a semiconductor integrated circuit element (a semiconductor device) from a substrate-like sample such as a semiconductor wafer, the above-described plasma processing apparatus has been conventionally used. In a process of manufacturing such a semiconductor wafer, miniaturization of the element has been advanced in order to achieve a request such as improvement of performance of the element and cost saving.
In the conventional miniaturization of the semiconductor devices, the number of elements that can be manufactured per one sheet of the semiconductor wafer is increased by two-dimensionally miniaturizing a structure of the circuit of the device to reduce the cost required for manufacturing one element, while improvement of performance such as a decrease in a required time for the device to calculate or input/output signals, or power consumption has been plotted by shortening a wire length. However, it is said that such the two-dimensional miniaturization of the structure of the circuit of the device has been approaching the limit and other technologies such as an application of a new material or a three-dimensional element structure have been under development in recent years. Meanwhile, with such the change of the material or the structure of the circuit, difficulty in manufacturing semiconductor devices is increased, and an increase in the manufacturing cost becomes a serious problem.
Therefore, to achieve cost saving in manufacturing, an expansion in a diameter of the semiconductor wafer used in manufacturing of the device from 300 mm to 450 mm has been considered. An area of the wafer having the diameter of 450 mm is 2.25 times the area of the wafer having the diameter of 300 mm and, as a result of the fact that a larger number of wafers can be manufactured, the manufacturing cost per one device can be reduced assuming the manufacturing cost per one sheet is equivalent.
In realizing the manufacturing of the device using the semiconductor wafer having such a large area, a technology that realizes uniform processing of the semiconductor wafer in a larger region than before is required for the plasma processing apparatus. Especially, a decrease in non-uniformity in a radial direction and a circumferential direction of plasma formed in the processing chamber, which should be made larger to accommodate the semiconductor, wafers having a larger diameter, is required.
Technologies using a circularly polarized wave as an electric field for forming plasma to decrease such non-uniformity of distribution of density and intensity of the plasma in the processing chamber are conventionally known. As examples of such conventional technologies, technologies disclosed in JP-A-2011-077292 and JP-A-2011-176146 are known.
In these prior-art documents, a circularly polarized wave generator is disclosed, which can optimally adjust an axial ratio of a circularly polarized wave, even if a reflection wave is returned to the circularly polarized wave generator from the plasma having a change in its characteristic due to a change in a voltage, or the density or the intensity of the plasma that is a dielectric as a load formed in the processing chamber, corresponding to the change. Here, the axial ratio of the circularly polarized wave means a ratio of a minimum value to a maximum value of an electric field of a circularly polarized wave, which rotates during one cycle period of the circularly polarized wave of a specific frequency. Further, JP-A-2011-077292 discloses that a monitor unit which detects an axial ratio of a circularly polarized wave is provided and the axial ratio of the circularly polarized wave is optimally adjusted according to an output from the monitor unit.
Further, JP-A-2003-110312 discloses an invention in which a matching box is arranged on a waveguide path (a waveguide) between a circularly polarized wave generator and a processing chamber so that the reflection wave originated as being emitted from an end portion of the waveguide, then being reflected on the processing chamber side, and being returned to the waveguide is prevented from entering the circularly polarized wave generator; it discloses that prevention of the reflection wave by the matching box can prevent deterioration of the axial ratio of the circularly polarized wave.
Further, JP-A-H02-230728 discloses a technology in which a plurality of rod-like members made of a conductor, insertion lengths of which into a circular waveguide are variably adjustable are arranged and the distribution of the electric field in the processing chamber is adjusted by appropriately adjusting the insertion lengths of these rod-like members, so that non-uniformity of distribution of an etching rate of a sample is decreased. Especially, this prior-art document discloses that conductor rods inserted at a plurality of different locations with respect to a traveling direction of the microwave are provided in an axial direction of the circular waveguide and reflection of the electric field traveling from the waveguide to the processing chamber on the processing chamber side is suppressed, so that the non-uniformity of processing can be improved.